Several techniques can be used to “print” a solid object layer by layer. In sintering, a thin layer of powdered metal or thermoplastic is exposed to a laser or electron beam that fuses the material into a solid in designated areas and a new coating of powder is laid on top and the process repeated. Parts can also be built up with heated plastic or metal extruded or squirted through a nozzle that moves to create the shape of one layer, after which another layer is deposited directly on top, and so forth.